This invention relates to a weighing machine which weighs a plurality of products inclusive of their tare weights and selects an optimum combination such that the total of the net weights of the selected products is the closest to a given target weight.
There have been known combinational weighing machines (as disclosed, for example, in Japanese Utility Model Publication Jikkai 4-36428), having many weight detecting units for weighing products comprising one or more articles such as salmon slices and adapted to combine a plurality of them such that the total weight detected by them is the closest to a given target weight value. The products from the selected plurality of weight detecting units are, for example, boxed and shipped.
In the case of already packaged products, however, the total weight obtained by such a weighing machine includes the tare weights. If the packaged products are vacuum-packed salmon slices, for example, the tare weights may be large enough to be non-negligible. Thus, tare weights must be subtracted and net weights of products must be obtained accurately when a large number of already packaged products are put in a box for a commercial purpose. Prior art weighing machines could not handle a situation like this because the net weights could not be ascertained.
In view of the above, it is an object of the present invention to provide a combinational weighing machine which subtracts tare weights and hence can obtain a combination of products such that the total of their net weights exclusive of their tare weights approaches a given target weight value even where the products are already packaged.
Another object of the invention is to provide such a combinational weighing machine capable of reducing the error due to tare weights even in situations where there are fluctuations in the numbers of products weighed by the individual weight detecting units or the total number of products finally to be put in a box.